Active segments along the North Anatolian Fault system in the Sea of Marmara

High-resolution multibeam and seismic reflection data collected during several oceanographic expeditions allowed us to compile an updated morphotectonic map of the North Anatolian Fault below the Sea of Marmara. We reconstructed kinematics and geometries of active fault segments at 10 ka time-scale, an interval that includes several earthquake cycles, taking the base of the latest marine transgression as a stratigraphic marker. Given the high deformation rates relative to sediment supply, most active tectonic structures have a morphological expression at the seafloor, even in the presence of composite fault geometries and/or overprinting due to mass-wasting or turbidite deposits. In the frame of the right-lateral strike-slip domain characterizing the North Anatolian fault system, three types of deformation are observed: almost pure strike-slip faults, mainly oriented E-W; NE/SW-aligned axes of transpressive structures; NW/SE-oriented trans-tensional depressions. Fault segmentation occurs at different scales, but main segments develop along three major right-lateral oversteps, which delimit main fault branches, from east to west: i) the transtensive Cinarcik segment; ii) the Central (East and West) segments; iii) the westernmost Tekirdag segment. We performed a quantitative morphometric analysis of the shallow deformation patterns observed by seafloor morphology maps and high-resolution seismic reflection profiles along the entire basin, to determine the nature and cumulative lengths of individual fault segments. These data were used as inputs for empirical relationships, to estimate maximum expected Moment Magnitudes, obtaining values in the range of 6.8 to 7.4 for the Central, and 6.8 to 7.1 for the Cinarcik and Tekirdag segments, respectively. We discuss such findings considering analyses of inherited geological structures, historical catalogs, and available paleoseismological studies for the Sea of ​​Marmara region, to formulate reliable seismic hazard scenarios.